\(\bullet \)  Data Collection and Preprocessing: refers to the block represented by the set of components (labels [baseline=(char.base)]
shape=circle,draw,text=black, scale=0.65, fill=none,fill opacity=2, inner sep=0.3pt] (char) 1.0;, [baseline=(char.base)]
shape=circle,draw,text=black, scale=0.65, fill=none,fill opacity=2, inner sep=0.3pt] (char) 2.0; and [baseline=(char.base)]
shape=circle,draw,text=black, scale=0.65, fill=none,fill opacity=2, inner sep=0.3pt] (char) 3.0;, Figure REF ). The input to the block are Bug Repositories extracted from their XML schema. First, component Metadata XML Parser [baseline=(char.base)]
shape=circle,draw,text=black, scale=0.65, fill=none,fill opacity=2, inner sep=0.3pt] (char) 1.0; parses the metadata. The extracted metadata are: i) Pre-defined attributes of the bug and ii) Free-form text that includes bug comments. Second component, Local Bug Database [baseline=(char.base)]
shape=circle,draw,text=black, scale=0.65, fill=none,fill opacity=2, inner sep=0.3pt] (char) 2.0; saves the metadata that are needed to establish relationships between the bug reports and discussion comments. Third component [baseline=(char.base)]
shape=circle,draw,text=black, scale=0.65, fill=none,fill opacity=2, inner sep=0.3pt] (char) 3.0;, pre-processes comments into four consecutive steps: i) Tokenization, ii) Normalization, iii) Stop-Word Removal, and iv) Stemming. Tokenization tokenizes text into terms. Normalization aims to eliminate punctuation, non alphanumeric symbols, converting terms to lowercase. Stop-Words Removal remove words that carry little meaning. We use a standard NLTK library to perform this task. Stemming reduces terms to its root form. For example, terms `crashing' and `crashed' reduce to their base term `crash'. We use the well-known Porter algorithm [1]} to perform this step. Same preprocessing steps also apply to component [baseline=(char.base)]
shape=circle,draw,text=black, scale=0.65, fill=none,fill opacity=2, inner sep=0.3pt] (char) 3.1; that represents terms formulated as user query inputs.
